We propose to extend and expand a research program of interdisciplinary studies on the immunological basis of schistosomiasis mansoni and Chagas' disease in Minas Gerais, Brazil. The program would integrate the expertise of five laboratories at four American universities with those of scientists at the FIOCRUZ Institute in Belo Horizonte, Brazil in a concerted effort to define the basic immunology, immunoregulation, and immunopathology of these diseases. Projects related to schistosomiasis would include examining the idiotypic basis of the regulation of cell proliferation and granuloma formation, and the assessment of the quality of the immune response to defined antigens in humans. Projects in Chagas' disease would include the basic immunopathology of the disease. All projects would be networked so that defined antigens and antisera would be shared, when appropriate, and regular meetings of all participating laboratories would be held to share data, assess progress in each project, and to facilitate technology transfer between the laboratories.